A COMPARATIVE STUDY ON THE PERFORMANCE OF BASE ISOLATION SYSTEMS WITH VARIABLE NEGATIVE STIFFNESS

摘要

Recent studies have shown that long-period ground motions greatly influence the conventional base isolation systems by producing large lateral displacements. This has prompted the need to modify base isolation systems for improving its performance. Current study focuses on varying the stiffness of a base isolation system for displacement mitigation of isolated objects. Negative stiffness is varied parametrically using different power functions in terms of the displacement response of the isolated objects. Equations of motion are formulated to study the response of the proposed system subjected to near-fault and long-period ground motions. Results of numerical simulation show that varying the stiffness with power function is able to effectively mitigate the displacement response. Results also indicate that high-order power function is effective in reducing the displacement response. However, acceleration response to near-fault ground motion tends to increase appreciably as the order of the power increases. An optimal order of power function satisfying the allowable limits of both the displacement and acceleration responses in practical use is proposed.